Elucidating genetic variation and mechanism of virus infection of Emiliania huxleyi via genomic approaches [Elektronische Ressource] / vorgelegt von Jessica U. Kegel

Jkegel

Description

Elucidating Genetic Variation and Mechanism of Virus Infection of Emiliania huxleyi via Genomic Approaches Dissertation zur Erlangung des Akademischen Grades eines Doktors der Naturwissenschaften - Dr. rer. Nat. - im Fachbereich 2 (Biologie/Chemie) der Universität Bremen vorgelegt von Jessica U. Kegel Bremen, März 2009 Erster Gutachter: Prof. Dr. Dieter Wolf-Gladrow Zweiter Gutachter: Prof. Dr. Allan Cembella Tag des öffentlichen Kolloquiums: Universität Bremen, 15. April 2009 Eidesstattliche Erklärung Hiermit erkläre ich nach § 6 Abs. 5 der Promotionsordnung der Uni Bremen (vom 14. März 2007), dass ich die vorliegende Dissertation (1) ohne unerlaubte Hilfe angefertigt habe, (2) keine anderen als die von mir angegebenen Quellen und Hilfsmittel benutzt habe und(3) die den benutzten Werken wörtlich oder inhaltlich entnommenen Stellen als solche kenntlich gemacht habe. __________________________Jessica Kegel .................................................................................1 .......................................1 !" ....................................3 # $ % !& & ..............................................................................................5 ’ & ........................................................................................................7 ’ " && ( & )! *& .....................................................

Sujets

• Biologie

Informations

• Publié par: universitat_bremen
• Publié le: 01 janvier 2009
• Nombre de lectures: 45
• Poids de l'ouvrage: 1 Mo

Extrait

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

Variation and Elucidating Genetic

Mechanism of Virus Infection of

Emiliania huxleyi via Genomic

Approaches

nossertatiDi

zur Erlangung des Akademischen Grades eines

chaften sturwissenaDoktors der N

- r. Nat. e- Dr. r

im Fachbereich 2 (Biologie/Chemie)

der Universität Bremen

von tgvorgele

Jessica U. Kegel

B 2009 en, Märzemr



Erster Gutachter: Prof. Dr. Dieter Wolf-Gladrow

Zweiter Gutachter: Prof. Dr. Allan Cembella

Tag des öffentlichen Kolloquiums: Universität Bremen, 15. April 2009

Eidesstattliche Erklärung

Hiermit erkläre ich nach § 6 Abs. 5 der Promotionsordnung der Uni Bremen (vom 14.

rtation vorliegende Disse 2007), dass ich die März

(1) ohne unerlaubte Hilfe angefertigt habe,

(2) keine anderen als die von mir angegebenen Quellen und Hilfsmittel benutzt habe

und

(3) die den benutzten Werken wörtlich oder inhaltlich entnommenen Stellen als

solche kenntlich gemacht habe.

__________________________

ssica Kegel eJ

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1 ........................................................................................................................1
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7 ...........................................................................................................................................................9
10 ..................................................................................................................10
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12 ....................................................................................................................................................................................12
13 ........................................................................................................................................................................................................................................................................................................................................36 14
........................................................................................................................................................................................65 94
............................................98 94
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104 ..................................................106 ...........................................................................................................................................................................................................................................................................................................124 121
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

Marine phytoplankton is represented by more than 20,000 microscopic
unicellular species of marine photoautotrophs (Falkowski et al., 2003) and is
ubiquitous in the world’s oceans which cover around 70% of the planet’s surface. Its
contribution to the global primary production is often disregarded because they
account for less than 1% of the global primary producer biomass (Falkowski et al.,
2004). However, it is responsible for more than 45% of the Earth’s annual net
primary production, which is roughly equal to the contribution of terrestrial plants
(Field et al., 1998). Grazing, viral attack, programmed cell death, and sinking into the
deep ocean balance the phytoplankton production (Falkowski et al., 1998).
Consequently, the system is characterized by a high turnover rate and a small
standing stock. Phytoplankton forms the base of the marine food chain and its growth
is primarily limited by light, nutrients and temperature (Falkowski & Raven, 2007).
Winter and autumn storms increase the availability of nutrients and thereby
enhancing the growth in particular of bloom formers including diatoms,
dinoflagellates and coccolithophores. These blooms can be observed near the coast
and/or in upwelling ecosystems (Smetacek, 1999, Smayda, 2000). Diatom-dominated
blooms occur mainly in turbulent, low-stratified waters during springtime (Smayda,
1997). In contrast coccolithophore-dominated blooms are found in nitrate-rich but

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phosphate-poor, well stratified waters during late spring and early summer (Haidar &
Thierstein, 2001). From about 250 coccolithophore species (Winter & Siesser, 1994),
the two species Gephyrocapsa oceanica and Emiliania huxleyi are the only bloom-
. s coccolithophoreformingThe importance of phytoplankton is due to its effect on global climate change
through its key role in regulating geochemical cycles such as the global carbon and
sulphur cycle. Hereby, marine phytoplankton is responsible for most of the transport
of organic matter to the deep ocean and the sediment (Falkowski et al., 2004) thus
impacting on atmospheric carbon dioxide (CO2) (Westbroek et al., 1993). In this
context the phytoplankton functional groups including coccolithophores also as well
as dinoflagellates, diatoms and cyanobacteria are of major importance (Falkowski et
al., 2004). In the process of photosynthesis carbon dioxide is incorporated into
particulate organic carbon (POC). Around 45 gigatons of POC are produced annually.
More than a third is exported to the ocean interior (Falkowski et al., 1998). A
combination of two fundamental processes, the physical and the biological carbon
pump, is responsible for the partitioning of CO2 between atmosphere and ocean. The
physical or so-called solubility pump describes the vertical carbon flux due to
differences in CO2 solubility of warm and cold water (Ito & Follows, 2003). The
biological pump can be sub-divided into the organic carbon pump and the carbonate
pump. The term “organic carbon pump” refers to the photosynthetic production of
POC in the surface ocean and its sinking to depth (Volk & Hoffert, 1985). The
carbonate pump includes the production of calcium carbonate (termed calcification)
by marine organisms (mainly coccolithophores and foraminifera) and its subsequent
transport to depth (Rost & Riebesell, 2004). Although both biological carbon pumps
remove carbon from the surface ocean, they have, on the production level, opposite
effects on the CO2 concentration of surface waters as explained in the following.
Photosynthesis consumes carbon in the form of CO2, thus reducing the dissolved
inorganic carbon (DIC) of the water without affecting total alkalinity (TA). This
shifts the carbonate system towards lower CO2 concentrations and higher pH.
Calcification consumes carbon in the form of CO32-, thus reducing both DIC and TA
in a 1:2 ratio. This shifts the carbonate system towards higher CO2 concentrations and
lower pH. Therefore the overall ratio of photosynthesis to calcification determines
whether a plankton community increases or decreases CO2 concentration of sea

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surface water. Another important difference of the two biological carbon pumps is the
preservation of the exported calcium carbonate that is buried in the sediments and
eventually subducted (Van Capellen, 2003).
Coccolithophores also play an important role in other element cycles, e.g. the
calcium cycle (De La Rocha & DePaolo, 2000) and the sulphur cycle (Malin et al.,
1994). When subject to grazing or during viral infection, E. huxleyi, a prolific
coccolithophore, produces high amounts of dimethylsulfoniopropionate (DMSP), an
important component in the sulphur cycle (Keller, 1989, Malin et al., 1992). DMSP is
the precursor of the trace gas dimethyl sulfide (DMS), its emission may contribute to
marine cloud formation and climate regulation (Andreae, 1990, Malin et al., 1992,
Liss et al., 1997, Stefels et al., 2007).
Besides their importance in biogeochemical and nutrient cycles, marine
phytoplankton is also intensively studied due to its contribution to biodiversity, value
as a gene pool in times of global biodiversity loss (Pimm et al., 1995), and as a
6). tural products (Shimizu, 199apotential source of n

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Coccolithophores are unicellular, marine algae belonging to the division of
Haptophyta and the class Prymnesiophyceae (Edvardsen et al., 2000). One prominent
feature of the coccolithophores is the a